Metal forming

ABSTRACT

A method of sealing a metallic tubular workpiece by rotating the workpiece relatively to a welding torch arranged transversely with respect to the axis of the workpiece, the speed of rotation of the workpiece relative to the torch being increased while the current fed to the torch is reduced so that the workpiece is cut into two portions, at least one having a sealed end closure formed by recasting of the metal of the workpiece melted by the torch.

United States Patent inventor Philip [In Dark Thursu. Caithness. Scotland Appl No. 593M113 Filed Nov. 9, i966 Patented July 13, 1971 Assignee United Kingdom Atomic Energy Authority London, England Priority Nov. 15, 1965 Great Britain 48477/65 METAL FORMING 9 (Ilaims, 2 Drawing Figs.

U.S.Cl 219/137, 29/470, 219/61 Int. Cl 823k 9/00 Field 01 Search 219/137,

[56] References Cited UNITED STATES PATENTS 3,346,717 10/1967 Pugh et a1. 219/121 2,309,561 1/1943 Westin et a1. 219/149 2,313,068 3/1943 Heineman..... 219/149 2,322,444 6/1943 Heath 219/149 2.391717 4/1946 Westin 219/149 3,067,321 12/1962 Westin etal. 219/152 Primary Examiner-Joseph V. Truhe Assistant Examiner-C. L. Aibritton Attorney-Larson, Taylor & Hinds ABSTRACT: A method of sealing a metallic tubular workpiece by rotating the workpiece relatively to a welding torch arranged transversely with respect to the axis of the workpiece, the speed of rotation of the workpiece relative to the torch being increased while the current fed to the torch is reduced so that the workpiece is cut into two portions, at least one having a sealed end closure formed by recasting of the metal of the workpiece melted by the torch.

PATENTED JUL 7 312m 59? SHEET 1 OF 2 butt weld formed by an argon arc-welding process. The use of 30 these welded end caps presents difficulties when the fuel elements are of small size in cross section, such as those referred to as fuel element pins. These difficulties are associated with various factors which include the need for precision in control I of weld penetration, the desirability of minimizing the zone affected by weld heat, the fact that abrupt changes in cross section occur in the immediate vicinity of the weld, and grain growth in the welded components.

According to the present invention a method of sealing a metallic tubular workpiece using a welding torch arranged transversely with respect to the axis of the workpiece is characterized in that the workpiece is supported to either side of the torch and in that with relative rotation being established between the torch and the workpiece and an are being struck between the torch and the workpiece the speed of relative rotation is increased while the current fed to the torch is reduced, so that the workpiece is cut into two portions, at least one having a sealed end closure formed by recasting of the metal of the workpiece in the region of the are. In order to smooth off .nt: seal weld thus formed and to round off external and internal sharp comers between the seal weld and the main body of the workpiece is is preferable to perform a second weld run with the welding torch set at the edge of the seal weld. This second weld run is also carried'out under reducing current conditions and increasing speed of rotation.

The invention also resides in a workpiece sealed by the method of the preceding paragraphs.

FIG. l is a partially schematic plan view of a conventional lathe having elements mounted thereon for carrying out the method of the present invention.

FIG. 2 illustrates a typical program for carrying out the method of the present invention.

By way of example the invention is described below in relation to its application in the manufacture of nuclear reactor fuel elements.

As shown in FIG. 1 of the drawings a workpiece in the form of a length of metal tubing is used, the tubing 1 being typically made of stainless steel and having for example an internal diameter of 0.200 inches and a wall thickness of 0.0l5- inches. The workpiece is mounted for rotation in a welding machine in the form of a modified lathe 2, the tubing I being supported in passage through the chuck 3 of the lathe headstock 4 and one end also being supported in the lathe tailstock 5. The tubing I is also fitted with two copper chills 6. Between the two copper chills 6 a welding torch 7 is arranged transversely with respect to the axis of the workpiece, that is to say with the axis of its electrode 8 lying perpendicular to the longitudinal axis of the tubing 1. The torch 7 is of the gas-shielded type employing argon or helium and mounted from the lathe bed 9 so that it can be moved to adjust the distance between the electrode 8 and the tubing I. The machine has a control unit enabling a programmed operation involving change of speed and current to be carried out, a typical program being represented graphically in FIG. 2.

In sealing the workpiece the tubing I is rotated about its longitudinal axis by the lathe drive motor while the torch 7 remains stationary, an argon or helium arc is struck between the electrode 8 and the tubing 1 while the appropriate shielding gas is fed through the workpiece and the speed of rotation of the tubing 1 is increased while the welding current fed to the torch 7 is reduced. The programmed operation used is typically as shown in the drawing. In this way the workpiece is cut into two portions, that supported by the chuck 3 having a sealed end closure formed by recasting of the metal of the tu bing I in the region of the are.

In order to smooth off the sealed end of the workpiece and to round off external and internal sharp corners between the sealed end and the main body of the workpiece it is preferable to carry out a second weld run on the workpiece with the torch electrode 8 set at the edge of the sealed end of the workpiece. The second weld then is also carried out with increase of speed of rotation of the workpiece while the welding current fed to the torch 7 is reduced. The following are specific examples of welding sequences carried out according to the method of the invention.

EXAMPLE] workpiece Austenitic stainless steel AISI 3 I 6 tubing Welding torch tungsten electrode l/32 inch diameter containing 2 percent Thoria Electrode setting (first and second weld runs) 0.018 inch to 0.915 inch from workpiece Shielding gas flow (first weld run only) l5 cubic feet per hour through the torch 5 cubic feet per hour through the workpiece Chill settings Chills set 5/l6 inch apart and the electrode set at one-eighth inch from the chill embracing the length of the tube which is to be sealed off FIRST WELD Current (amp) Workplace workpiece (dla. 0.2m" (dla. 0.326") Hot-i2. Vert. Speed Action (rev/min.) Argon Helium Argon ti. 1 0 0 0 0 8. I 22. 2 14. 2 35. 2 39.4

Speed 3 6. 8 22 2 14. Q 36. 2 39.4

.0 Current step 1. 6. 8 21.8 13. 8 34. 8 39.0v 18.0 Current. step 2 6. 8 l9. 6 l2. 6 32. 8 37.0 15.2 Speed 4 10.3 19. 6 12. 6 32. 8 37. 0 10.0. Step1-.. 10.3 18.4 11.8v 31.6 36.8 17.6. Step L 10. 3 I1. 2 1:. 0 3G. 4 3446 17.2.. Speed ll 13. 6 l7. 2 1X. 0 30. 4 3446 18.0.. Step 5. 13. 6 I6. 0 9. 6 29. 0 33.2 18.2.. Speed 6 I7. I 16. 0 9. 6 29.0 33.2v 19.0. Current 08. 17.1 0 0 0 0 19.4... Rotation 0th... 0 0 0 0 0. set 0 0 0 0 D SECOND WELD Current (amp) Workplace (dla. 0.230") Workplace Speed (dla. 0.325"), Actlon (rwlmln) Argon Hnllum argon Time (sec):

0 0 0 0 1 0 0 0 0 2 0 0 O 0 3 Current on 0 5. 2 5. 2 12. B 5.2 Rotation on. 4. 75 5. 2 l5. 2 12. B 9.2 Speed 2. 5.1 5. 2 5. 2 12. B 11. Speed 3. 5. 45 5. 2 5. 2 12. 8 13. Current step 1. 5. 45 4. B 4. 8 12.0 13. Speed 4 5. 75 4. B 4. 8 12. 0 14. 5. 75 4. 4 4. 4 11. 2 15. 5. 75 3. 8 4.0 9. 6 15. 6. S5 3. 8 4. 0 9. 6 20. 6. 85 3. 4 3. 6 8. 8 21. 6. 85 2. 4 3. 2 6. 2 22. 10. 9 2. 4 3. 2 6. 2 240 Current off. l0. 9 0 0 0 24. Rotatlon ofl. 0 0 0 0 24.4 Raset 0 0 0 9 EXAMPLE ll SECOND WELD The baslc deta|ls are as for example I wnh the excepuon of Speed [rem] g f gfi g fi the chill settings for the first weld run. In [his case for the first Action min.) 0.250"), argon weld run the chills are set 7/16 inch apart and the electrode set Time (sec) at 1/16 Inch from the C111 embracmg the length of tube which g g 1510 besealedoff. 0 0 2.2 Current on 0 5. 2 4. Rotatlon on... 4. 75 5. 2 10. Speed 2. 5.1 5. 2 12. Speed 3- 5. 45 5. 2 FIRST WELD 14 Current step I 5. 45 6.2 15 Speed 4- 5. 75 6. 2 Current amps 15. Current step 2. 5. 75 5. 8 Speed (revJ (workplace dia. 15. Current step 3. 5. 75 5. 2 Action min.) 0.230"), argon 17. Spaed 5 6. 85 5. 2 i7. gun-am step g. g-g Timfl 8- urren 5 ep 0. (sec 0 0 18. Speed 6 10. 9 3. 8 1. 0 0 19 Current 011.. 10.9 0 2. 0 0 19. Rotation ofl. 0 0 2. 5. 1 0 21 Reset 0 0 4. 6. 1 19. 2 10 6. 19. 2 12. 6. 8 19. 2 14 unent step 1. 6. 8 18. B 15 Cumnt step 2. 6. 8 l6. 8 15. ipeed 4 10. 3 16. B 16. urrent step 3. 10. 3 15. 6 45 17. Current step 4. l0. 3 l4. 4 17.2 Speed 5 13. 6 14. 4 18 Current step 5. 13. 6 12. 8 18.2 Speed 6 17. 1 12.8 19, Current 011..... 17.1 0 EXAMPLE Ill 19. Rotation ofl. 0 0 21 Reset 0 0 The basic details are as for example 1.

TABLE EXAMPLE III Wor lees 0.23 dla.

wel ing in argon Flxst weld Second WBld Current Speed 'llme Currant Speed Time (590.) Actlon (amp) (socJl-ev.) ($60.) (amp) (sea/rev.)

0 1 Start O 0 0 0 0 1 0 0 1 0 0 2 0 0 2 0 0 3 0 0 3 0 0 3.2. Rotation 011--...- 0 9. 8 3. 8 0 12. 6 4.0. Current on 21. 8 9. B 4. 0 21. 8 12. 6 10.2 21. B 9. 3 4. 2 15. 8 12. 6 12,2 21.8 8.8 4.4 12. 2 12. 0 14.0 15. 8 B. 8 4. 6 10. 8 12. 6 15.0 12. 2 8. 8 10. 2 10. 8 11. 8 15,2 12.2 5.8 12.2 10.8 11.0 16.0- 10. 8 5. B 15. 2 10. B 9. 8 17. 9.4 5.8 10.0 9.4 9.8 17. 9.4 4. 4 17. 2 9.4 7. 3 1B. 8. 0 4. 4 19. 2 9. 4 5. B 19. 0 4. 4 2o. 0 8. 0 5. 8 a), 0 0 22.0 0 0 21.0 Reset 0 0{ 32 g 8 The workpiece u alloy Nimonic PEI sed in this example wa s oflhe nickel based 6, in the form oftubing.

FIRST WELD Current lees? Aetltm (amp). men (rem/min. Tlme (see):

0. Audible wernln 0 I. ..do 0 0 2. do 0 0 2.2 Rotation on 0 6. 1 4.0 Current on 18.0 6. l 10. 1s. 0 a a 12.2 18. o 6. s 14.0. Step 1 17. 6 o. 8 15.0 Step 15. s 6. 8 15.2 Speed 4 16. e 10. 3 16.0. Step 3-- 14. 4 10. 3 17.0 4 1a. 2 10. 3 17. 13. 2 13. 6 is. 11.8 13. s 19. 9. 0 13. a 20 e. 2 13. 6 an. e. 2 1d. 6 21. 4. 8 1e 6 22. 4. 8 23.

nrrent Speed Action (amp). argon (em/rev.)

Audible warning. 0 D

Speed 4. 6 5. l 11. 4. 6 5. 46 13. Step 1 4. 2 5. 46 13. Speed 4 4. 2 6. 75 14. Step 2. 3. 8 5. 75 16.0 Step 8- 3. 0 6. 75 16.2..-. Speed 3.0 6.8 20.0 step 4-. 2.4 6.8 21.0 2. 0 o. a 22 2. 0 to. 9 24 0 9 24 0 0 24. 0 0

I claim:

welding torch arra nged transversely wit ular workpiece using a h respect to the axis of uck between the the relative speed of rotation ll to the torch ls reduced so that th portions,

metnlllc tubular workpleee n e workpiece ll fitted elther elde 3. A method claimed in cla' ng a sealed end closure made by g a sealed end closure made by fitted either side of the 

1. A method of sealing a metallic tubular workpiece using a welding torch arranged transversely with respect to the axis of the workpiece characterized in that the workpiece is supported to either side of the torch and in that with relative rotation being established between the torch and the workpiece and an arc being struck between the torch and the workpiece, the relative speed of rotation is increased while the current fed to the torch is reduced so that the workpiece is cut into two portions, at least one having a sealed end closure formed by recasting of the metal of the workpiece in the region of the arc.
 2. A method of sealing a metallic tubular workpiece as claimed in claim 1 wherein the workpiece is fitted either side of the torch with metal chills.
 3. A method of sealing a metallic tubular workpiece as claimed in claim 1 wherein a second weld run is made with the torch set at the edge of the sealed end closure as formed By the method of claim 1, an arc being struck between the torch and the edge of the sealed end closure, and relative rotation being established between the workpiece and the torch, the relative speed of rotation of the torch and workpiece being increased while the current fed to the torch is reduced.
 4. A tubular workpiece having a sealed end closure made by the method of claim
 1. 5. A tubular workpiece having a sealed end closure made by the method of claim
 2. 6. A tubular workpiece having a sealed end closure made by the method of claim
 3. 7. A method of sealing a metallic tubular nuclear reactor fuel element sheath using a welding torch arranged transversely with respect to the axis of the sheath characterized in that the sheath is supported to either side of the torch and in that with relative rotation being established between the torch and the sheath and an arc being struck between the torch and the sheath, the relative speed of rotation is increased while the current fed to the torch is reduced so that the sheath is cut into two portions, at least one having a sealed end closure formed by recasting of the metal of the sheath in the region of the arc.
 8. A method of sealing a metallic tubular nuclear reactor fuel element sheath as claimed in claim 7 wherein the sheath is fitted either side of the torch with metal chills.
 9. A method of sealing a metallic tubular nuclear reactor fuel element sheath as claimed in claim 7 wherein a second weld run is made with the torch set at the edge of the sealed end closure as formed by the method of claim 7, an arc being struck between the torch and the edge of the sealed end closure, and relative rotation being established between the sheath and the torch, the relative speed of rotation of the torch and sheath being increased while the current fed to the torch is reduced. 